2017 Chevrolet Silverado - Image: ChevroletAmerica’s auto industry is expected to report today its seventh consecutive month of decline, a drop of at least 5 percent based on forecasts and some sharp declines from three of the largest manufacturers: GM, Ford, and FCA.

Incidentally, GM, Ford, and FCA are America’s three biggest sellers of pickup trucks, and for the most part, pickup trucks are allowing a degree of buoyancy at the Detroit Three despite plunging passenger car sales. But after pickup truck sales rose 4 percent through the first-half of 2017, pickup truck sales declined in July 2017. Slightly. Somewhat.

And it was mostly General Motors’ fault.

Midsize pickup truck volume actually grew 4 percent in July 2017, a gain of 1,503 units propelled by improvements at Toyota, Chevrolet, and Nissan. Sales of the two lowest-volume pickup trucks in America — the Honda Ridgeline and GMC Canyon — declined by 1,703 units. Yet even with those dropoffs, the midsize pickup segment grew its share of the pickup truck market to 18 percent in July 2017, up from 17 percent one year ago.

Full-size pickups, however, were down 2 percent even as the top-selling Ford F-Series reported its seventh increase in the last eight months. F-Series sales are up 8 percent this year, on track for a twelve-year high of roughly 890,000 sales. Ford says the F-Series’ average transaction prices were $2,500 higher in July 2017 than in July 2016, powered in large part by surging F-Series Super Duty demand and ATPs in the Super Duty range that rose $4,000, year-over-year, to $55,000.

Ram sales were essentially flat, falling only 101 units behind July 2016’s sales pace. Ram is on track for more than 500,000 pickup truck sales in 2017. Toyota’s 1-percent Tundra uptick in July represented its third consecutive monthly improvement after beginning the year in steady decline. Nissan’s 232-percent Titan increase, relative to a particularly slow period from 2016 prior to complete Titan availability, resulted in 2,648 additional sales for the full-size truck category.

But at General Motors, where full-size truck volume tumbled 14 percent, America’s full-size pickup truck segment lost 10,615 sales in July 2017, year-over-year. Exclude GM from the equation and full-size pickup volume jumped 5.5 percent in July. Exclude GM’s four trucks from the entire picture and U.S. truck sales were up 4.6 percent in July.

GM’s knack for reducing the overall pickup truck category’s rate of growth was nothing new in July. Throughout 2017, GM has seen its truck volume fall by nearly 31,000 sales, a huge departure from a category that, GM excluded, is up by more than 84,000 units.

July’s declines were the tenth in the last twelve months for both the Chevrolet Silverado and GMC Sierra. The pickup truck category has lost volume only twice in the last twelve months.

[Image: General Motors]

Timothy Cain is a contributing analyst at The Truth About Cars and Autofocus.ca and the founder and former editor of GoodCarBadCar.net. Follow on Twitter @timcaincars.